And a Twitter user on a service in the area, writing as the Rugby Rail Users Group, described trains "stacked" up unable to move, adding: "The ontrain announcement said landslide and derailment at Watford Junction, not good at all."

Services travelling in and out of London Euston station are heavily affected but there are no reports of any injuries, operator London Midland said.

Commuters at Euston posted pictures on social media of chaotic scenes, with all of the announcement boards blanked out as services were cancelled en masse.